Threatwatch: Drug-resistant TB looms even larger

Threatwatch is your early warning system for global dangers, from nuclear peril to deadly viral outbreaks. Debora MacKenzie highlights the threats to civilisation – and suggests solutions

The stakes just got higher in the fight against tuberculosis. This week the World Health Organization set ambitious targets for ridding the world of the disease. Yet drug-resistant TB is on the rise, and research just published shows we are doing little to slow it down. Most ominously, global spending on new drugs that will kill it has fallen – and the purse strings are expected to tighten.

12 million people in the world have TB, and it kills 1.4 million each year. At a meeting in Geneva, Switzerland, which took place between the 20 and 25 January, the WHO's member countries set out their plans to change that. Their goal is half as many cases, and a quarter as many deaths, by 2025 – and only 1.2 million cases, and 95 per cent fewer deaths by 2035.

Those are ambitious targets, especially as TB is becoming more and more resistant to the few antibiotics that work against it. Only a minority of people are not cured by established drugs regimes, but cases are steadily increasing, with a 65 per cent rise since 2006. There are some 650,000 cases of multi-drug-resistant or MDR TB worldwide, and 9 per cent of those resist almost all drugs (XDR TB).

The good news is that since 2005, the WHO has been coordinating a worldwide effort to find new TB drugs, and as of December 2013 two new classes of drug had been approved, the first for 40 years. These work against XDR TB. Yet more new drugs are needed and in 2013, for the first time since 2005, both public and private funding for research into new TB drugs fell.

Drug failure

Last week Keertan Dheda at the University of Cape Town in South Africa and colleagues published the first long-term follow-up of XDR TB, which showed that the drugs available in South Africa fail in 90 per cent of cases.

He found that of around 110 XDR TB cases treated in three South African hospitals, only 11 per cent were eventually cured. Nineteen people for whom treatment didn't work were discharged back into the community with active infection, where they survived up to 26 months, and at least one passed on the infection. "Therapeutic failure is occurring systematically on a country-wide level," says Dheda. "It is likely that XDR will become a larger percentage of total TB infections like MDR did."

South Africa isn't alone. XDR TB has now been discovered in 92 countries; it is especially bad in the former Soviet Union. Eventually, it will be everywhere, says Grania Brigden of medical aid group Médecins Sans Frontières (MSF).

The new targets are the latest in the WHO's Global Plan to Stop TB, launched in 2006. By making TB drugs more widely available, the programme has largely reached its 2015 goals, halving the death rate from the disease, and cutting global case numbers by 5 per cent.

But so few cases of MDR are recognised, and so rarely does the treatment work that the success rate in these cases is just 8 per cent, says Max O'Donnell of the Albert Einstein College of Medicine in New York. "Many of the rest are surviving longer than we thought and contributing to the spread of resistant strains."

Palliative care

A cure would be better than containment. Brigden says the few XDR cases so far found in rich countries would usually be treated until they were cured, with the newly developed drugs if necessary. MSF is successfully treating XDR with these in Armenia. The drugs are not yet available in South Africa, however.

"We've had encouraging early results with what would have been palliative cases," says Bridgen. However, she says resistance will grow against these too. At the Geneva meeting, she called for faster testing of new drugs and combinations. "It's incredibly worrying that there are no new TB drugs in early trials," she says.

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